The present invention relates to a method and apparatus for switching loop type transmission lines.
It is well known in two-station communication that the system is arranged such that the active line is switched to the stand-by line upon occurrence of abnormality in the transmission line.
It is also known that the above-mentioned method of switching the active line to the stand-by line can be applied also to multi-station communication using a loop type transmission line.
However, the conventional method does not carry out the switching for the overall transmission line, and there has not been realized a method which carries out the switching smoothly.